The visual pigment, rhodopsin, is highly and exclusively expressed in rod photoreceptors, with the temporal and spatial patterns of expression predominantly regulated at the level of transcription. Several transcription factors have been identified that can to bind to cis-elements within the rhodopsin promoter and transactivate expression in vitro. Mutations in two of these, Crx and Nrl, have been found in patients with degenerative retinal diseases, demonstrating the critical importance of precise regulation of rhodopsin expression for photoreceptor survival. Recently, a zinc-finger containing transcription factor, RKLF (retinal Kruppel-like factor), was identified by its ability to bind to a Sp1-consensus element within the rhodopsin proximal promoter. The proposed research will test the hypothesis that RKLF is a component of the transcriptional complex that regulates rhodopsin gene expression. Specifically, these studies will: (1) complete the sequence analysis of bovine, murine and human RKLF and determine the genomic structure; (2) characterize the size and tissue distribution of the mRNA using Northern blot analysis and in situ hybridization; (3) determine the affinity and specificity of RKLF/DNA interactions; and (4) test the hypothesis that RKLF can transactivate the rhodopsin promoter in vitro.